Section 15. If any officer of a city or town having charge of any land, easement or right taken for such city or town, otherwise than by purchase, notifies the city council or the selectmen that, in his opinion, such land, easement or right, or part thereof, is no longer required for public purposes, and if thereafter the city council or the inhabitants of the town by a two thirds vote authorize the conveyance of such land, or of part thereof, or the abandonment of such easement or right, or part thereof, and specify the minimum amount to be paid for such conveyance or abandonment, the mayor or the selectmen may, for such amount or a larger amount, and upon such other terms as the mayor or selectmen shall consider proper, convey said land, or part thereof, by deed, or declare said easement or right, or part thereof, to be abandoned. Such declaration, being recorded in the registry of deeds for the district where the land is situated, shall extinguish the easement or right, or part thereof.

No land heretofore or hereafter acquired by eminent domain by one city or town within the limits of another city or town shall be conveyed under this section unless the mayor or selectmen authorized to convey such land offer to convey such land to the city or town wherein such land lies for the minimum amount specified as aforesaid, nor unless such offer is not accepted within six months after notice thereof is given to the mayor or selectmen of the city or town wherein such land lies by the mayor or selectmen authorized to convey, nor unless such conveyance is made within three months after the expiration of said six months. Land so offered to a city or town wherein it lies may be purchased by such city or town whether or not needed for the municipal purposes of such city or town, and, if so purchased and if such land is not needed for municipal purposes, it shall be disposed of as such city or town shall determine.